The present disclosure generally relates to a surgical apparatus for fusing adjacent bone structures, and, more particularly, to a threaded, barrel-shaped apparatus and method for fusing adjacent vertebrae.
The fusion of adjacent bone structures is commonly performed to provide for long-term replacement to compensate for vertebral subluxation typically caused by severe trauma to the spine, degenerative or deteriorated bone disorders, e.g., osteoporosis, abnormal curvature of the spine (scoliosis or kyphosis) and/or weak or unstable spine conditions typically caused by infections or tumors. In addition, an intervertebral disc, which is a ligamentous cushion disposed between adjacent vertebrae, may also undergo deterioration or degeneration as a result of injury, disease, tumor or other disorders. The disk shrinks or flattens leading to mechanical instability and painful disc translocations, commonly referred to as a xe2x80x9cslipped discxe2x80x9d or xe2x80x9cherniated discxe2x80x9d.
Conventional procedures for disc surgery include partial or total excision of the injured disc portion, e.g., discectomy, and replacement of the excised disc with biologically acceptable plugs or bone wedges. The plugs are driven between adjacent vertebrae to maintain normal intervertebral spacing and to achieve, over a period of time, bony ingrowth or xe2x80x9cfusionxe2x80x9d with the plug and opposed vertebrae.
Alternatively, at least one metallic fusion cage may be is inserted within a tapped bore or channel formed in the intervertebral space thereby stabilizing the vertebrae and maintaining a pre-defined intervertebral space. A pair of fusion cages may also be implanted within the intervertebral space. After a period of time, the soft cancellous bone of the surrounding vertebral bone structures infiltrates the cage through a series of apertures disposed within its external wall and unites with bone growth inducing substances disposed within an internal cavity to eventually form a solid fusion of the adjacent vertebrae.
The present disclosure relates to a barrel-like fusion implant apparatus for facilitating fusion of adjacent bone structures. The apparatus includes an implant member which is positioned between adjacent opposed bone structures and which defines a longitudinal axis and first and second longitudinal ends. The implant member includes an outer wall dimensioned to engage the opposed bone structures upon positioning therebetween in supporting relation therewith. The outer wall includes at least one thread for facilitating positioning of the implant member between opposing bone structures. Preferably, the implant member also includes an intermediate portion which defines a cross-sectional dimension transverse to the longitudinal axis which is greater than respective cross-sectional dimensions of the first and second longitudinal ends of the implant member.
The present disclosure also relates to a method of fusing adjacent vertebrae utilizing a barrel-like fusion cage. The method includes the steps of: 1) accessing a space defined between the vertebrae; 2) providing a barrel-like fusion cage as described above; 3) advancing one of the first and second ends of the fusion cage into the space between adjacent vertebrae and positioning the cage in contact with the adjacent vertebrae; and 4) permitting bone ingrowth into contacting surfaces of the fusion cage to facilitate fusion of the adjacent vertebrae.